Circuitbuilding Do-It-Yourself For Dummies®

Chapter 11. Meet the Test Equipment

No carpenter or mechanic can get by without measuring devices in the tool-box. Both have to measure length, carpenters measure angles, mechanics measure pressure, and so forth. They can't do their jobs without them and it's the same for electronic-ers like you. This chapter shows you electronic test equipment, both basic and advanced. We also introduce and explain the most marvelous piece of equipment — the oscilloscope.

What to Measure

There are four basic types of electronic measurements: voltage, current, resistance, and time or frequency. No matter what type of electronics you're working with, all of these types will be important sooner or later and sometimes at the same time! If you have some experience with electronics, you can probably skip the following discussion of each measurement.

• Voltage: This is what causes electrons to move and create current. Voltage (also called potential) is analogous to pressure in a water pipe. More pressure (voltage) causes more electron motion (current). Voltage, like pressure, is always measured between two points in a circuit. One point may be ground potential, using a reference connection to the Earth as one of the points. If voltage is only specified as a value, without identifying the points between which it is measured, you may assume that the voltage is measured with respect to ground or a common reference point, such as a power source's negative or neutral terminal. The units of voltage are volts, abbreviated ...